The communications industry is rapidly changing to adjust to emerging technologies and ever increasing customer demand. This customer demand for new applications and increased performance of existing applications is driving communications network and system providers to employ networks and systems having greater speed and capacity (e.g., greater bandwidth), and to use storage area networks (e.g., SANs, VSANs) such as those implemented using Fibre Channel.
Fibre Channel is logically a bidirectional point-to-point serial data channel, structured for high performance. Fibre Channel provides a general transport vehicle for higher-level protocols such as Small Computer System Interface (SCSI) command sets, the High-Performance Parallel Interface (HIPPI) data framing, IP (Internet Protocol), IEEE 802.2, and others. Fibre Channel frames contain 24-bit address identifiers, which identify the frame's source and destination ports, with a domain identifier (Domain_ID) being the highest octet of the address. Each switch in a fibre channel switched fabric is assigned one or more unique domain identifiers using a two-step process. First, one switch, called Principal Switch, is selected from the switches of the fibre channel switched fabric. Then, the Principal Switch assigns the domain identifiers to the other switches of the fibre channel switched fabric. Address assignment within a domain is performed by the switch to which that domain identifier is granted.